A. Field of the Invention
The invention relates to a security element having a color filter, a document of value having such a security element as well as a manufacturing method of such a security element.
B. Related Art
Objects to be protected are often equipped with a security element, which allows the object to be authenticity-checked and at the same time serves as a protection against unauthorized reproduction.
Objects to be protected are for example security papers, identity documents and documents of value (such as e.g. bank notes, chip cards, passports, identification cards, identity cards, shares, bonds, deeds, vouchers, checks, admission tickets, credit cards, health cards, etc) as well as elements for the product protection, such as e.g. labels, seals, packagings, etc.
For such security elements there are known different structures in order to achieve color-influencing effect. There can be employed interference filters, thin semi-transparent metal layers with selective transmission through plasma resonance effects, nanoparticles, micro-perforated metal foils and wire gratings, photonic crystals, metallic gratings with excitation of surface plasmon polaritons, wire gratings with exploitation of the resonance in TE polarization and subwavelength gratings metallically vapor-deposited at an oblique angle, so-called z gratings.
The production of finely structured multi-color motifs, however, has so far only been known for z gratings. For this purpose, it is necessary to vary at least one structure parameter laterally within the motif region in order to thereby produce the desired color at the target positions. The production of the color through z gratings is very suitable in transmission. In reflection, however, the color contrast is only little pronounced and only a relatively small region of the color space can be represented.
On these premises, it is the object of the invention to provide a security element having a color filter with which an as large a region of the color space as possible can be covered and which is suitable both for reflection and for transmission.